The invention set forth in this specification relates to the combination of what may be referred to as an extendable crane and a conduit for use in conveying material such as concrete.
It is well known to use conduits for conveying various materials such as concrete in combination with various types of cranes in the construction industry. Such combined structures are commonly employed to convey concrete to various locations in buildings, bridges and the like which are under construction. These structures may, however, be utilized for a wide variety of other purposes. The cranes employed with such structures may be constructed in a wide variety of different manners. It is considered that there is a lack of complete uniformity as to the terminology to be used in describing these various types of cranes. Many such cranes are of an extendable variety so that they can be extended in delivering material to any desired distance and/or height. Most commonly the cranes utilized in delivering pulverant material such as concrete are of two different types.
Probably the most common of these types may be referred to as rotary cranes employing a sectionalized swing-boom. In some of such cranes the sections of the boom are pivoted to one another so that the booms may be extended to an operative position by rotating the boom sections relative to one another. For many applications it is considered desirable to construct such cranes utilizing individual sections which may be moved linearly relative to one another. Frequently such extendable cranes are constructed so that the boom sections are telescoped within one another. Cranes of this type are commonly mounted on trucks in the construction industry so that they may be readily transported in a collapsed type configuration from one job site to another.
So-called hammerhead cranes constructed so as to utilize a rotating, counter-balanced, cantilevered boom section supported by a turntable on a tower are also commonly utilized in delivering concrete and the like. Such cranes employ one or more trolleys along the cantilevered boom and move these trolleys back and forth relative to the turntable and/or tower in delivering material to various locations.
A number of different conduit structures have been employed with these various types of cranes in delivering cement and other materials. Flexible hoses or conduits have frequently been employed in combination with these types of cranes. Such conduits are considered disadvantageous for this type of use for a variety of reasons which are considered relatively unimportant to an understanding of the present invention. In passing it should, however, be noted that such flexible conduits do not always fold in a convenient manner and are apt to move during the transportation of a crane to which they are attached.
The recognition of the problems encountered with flexible concrete delivery conduits has resulted in the development of a variety of different structures. It has been proposed to utilize flexible and rigid conduits in connection with sectionalized boom cranes in which the individual crane sections are rotated or pivoted with respect to one another in structures in which rotary joints in the conduit are located so as to be aligned with the axes of rotation between the boom sections. Structures of this type are considered to be somewhat undesirable from a commercial standpoint because of the inherent limitations as to the manner in which this type of crane structure can be operated.